recipe: new recipe to get a free network port

setup.py

@@ -111,6 +111,7 @@ setup(name=name,
           'erp5testnode = slapos.recipe.erp5testnode:Recipe',
           'firefox = slapos.recipe.firefox:Recipe',
           'fontconfig = slapos.recipe.fontconfig:Recipe',
+          'free_port = slapos.recipe.free_port:Recipe',
           'generate.mac = slapos.recipe.generatemac:Recipe',
           'generate.password = slapos.recipe.generatepassword:Recipe',
           'generic.cloudooo = slapos.recipe.generic_cloudooo:Recipe',

slapos/recipe/free_port.py

+##############################################################################
+#
+# Copyright (c) 2016 Vifib SARL and Contributors. All Rights Reserved.
+#
+# WARNING: This program as such is intended to be used by professional
+# programmers who take the whole responsibility of assessing all potential
+# consequences resulting from its eventual inadequacies and bugs
+# End users who are looking for a ready-to-use solution with commercial
+# guarantees and support are strongly adviced to contract a Free Software
+# Service Company
+#
+# This program is Free Software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 3
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+#
+##############################################################################
+
+import socket
+import netaddr
+
+class Recipe(object):
+  """
+  Uses the socket python standard library to get an unused port.
+
+  Notice : this recipe may still fail because of race condition : if a new
+  process spawns and use the picked port before the service for which it has
+  been generated starts, then the service won't start. Therefore, the result
+  would be the same giving an already-in-use port to the service.
+  """
+
+  def __init__(self, buildout, name, options):
+    self.minimum = int(options.get('minimum', 1024))
+    self.maximum = int(options.get('maximum', 49151))
+    self.ip = options.get('ip')
+
+    self.options = options.copy()
+
+    if netaddr.valid_ipv4(self.ip):
+      self.inet_family = socket.AF_INET
+    elif netaddr.valid_ipv6(self.ip):
+      self.inet_family = socket.AF_INET6
+    else:
+      # address family is unknown, so let's return a general purpose port
+      self.options['port'] = 0
+      return
+
+    self.options['port'] = self._getFreePort()
+
+  def _getFreePort(self):
+    """
+    Port number will be picked from a given range, smaller port first, then
+    incremented until a free one is found.
+    This algorithm thus returns always the same value with the same parameters in
+    a standard environment.
+    """
+    for port in xrange(self.minimum, self.maximum):
+      sock = socket.socket(self.inet_family, socket.SOCK_STREAM)
+      try:
+        sock.bind((self.ip, port))
+        break
+      except socket.error:
+        continue
+      finally:
+        sock.close()
+    else:
+      port = 0
+
+    return port
+
+  def install(self):
+    pass
+
+  def update(self):
+    pass

slapos/test/recipe/test_free_port.py

+import mock
+import socket
+import unittest
+
+from slapos.recipe import free_port
+
+class SocketMock():
+  def __init__(self, *args, **kw):
+    self.args = args
+    self.kw = kw
+    pass
+
+  def nothing_happen(self, *args, **kw):
+    pass
+
+  bind = close = nothing_happen
+
+import sys
+sys.modules['socket'].socket = SocketMock
+
+class FreePortTest(unittest.TestCase):
+  def afterSetup(self):
+    SocketMock.bind = SocketMock.close = SocketMock.nothing_happen
+
+  def new_recipe(self, **kw):
+    buildout = {
+      'buildout': {
+        'bin-directory': '',
+        'find-links': '',
+        'allow-hosts': '',
+        'develop-eggs-directory': '',
+        'eggs-directory': '',
+        'python': 'testpython',
+        },
+       'testpython': {
+         'executable': sys.executable,
+       },
+       'slap-connection': {
+         'computer-id': '',
+         'partition-id': '',
+         'server-url': '',
+         'software-release-url': '',
+       }
+    }
+    options = {
+      'ip': '127.0.0.1',
+    }
+    options.update(kw)
+    return free_port.Recipe(buildout=buildout, name='free_port', options=options)
+
+  def test_ifNoBusyPortThenMinPortIsAlwaysReturned(self):
+    recipe = self.new_recipe(minimum=2000)
+    self.assertEqual(recipe.options['port'], 2000)
+
+  def test_iterateUntilFreePortIsFound(self):
+    def bindFailExceptOnPort2020(socket_instance, binding):
+      ip, port = binding
+      if port != 2020:
+        raise socket.error()
+    SocketMock.bind = bindFailExceptOnPort2020
+    recipe = self.new_recipe(minimum=2000)
+    self.assertEqual(recipe.options['port'], 2020)
+
+  def test_returnsPort0IfNoPortIsFreeInRange(self):
+    def bindAlwaysFail(socket_instance, binding):
+      raise socket.error()
+    SocketMock.bind = bindAlwaysFail
+    recipe = self.new_recipe(minimum=2000, maximum=2100)
+    self.assertEqual(recipe.options['port'], 0)